The age of the earth is a creation day of the earth, measured by the periods of nights and days (Gen.1: 14-19).
Since the first day of the Jewish Calendar was an earth creation day, and this year of 2014 A.D is equal to the Jewish year of 5775. (Webster's New Collegiate Dictionary).
This year, the earth is 5775 (five thousand seven hundred seventy five) years old.

God, in Genesis, made it very clear that the earth and universe were created in 6 x 24 hours day periods and not 6 eras of time. In exodus 20 he confirmed this by saying that as he created everything in six days and rested on the seventh so should we also in our work day lives.
If we go along with the theistic evolutionists, then there were millions of years of evolution accompanied by death and suffering.This goes against God saying that his creation was very good (Gen 1:30). Also the process of evolution from microbes to man involves mutations coupled with natural selection. And mutations cannot lead to higher life forms only death. Natural selection only works on animal kinds to remove those which cannot cope with their environment. Natural selection therefore works on gross observable changes and not on subtle mutational changes.
The fossil record and geological changes seen today confirm the cataclysmic, worldwide Noahic flood and not the millions of years for their formation. The presence of carbon-14 (half-life 5,700 years) radioisotope in oil, diamonds and fossils confirm their 6,000 year history. There is evidence in the world of dinosaurs roaming the earth a few hundred years ago. Fresh tissues have been found in T Rex bones (reported in the Science journal about 5 years ago) indicating that they were unlikely wiped out 65 million years ago.
To conclude the scientific evidence confirms the accuracy of Biblical history. One cannot compromise the word of God in Genesis 1-10 without compromising the salvation and redemption that Christ earned for us at Calvary 2,000 years ago. It is no wonder that our 15-17 year old youth are leaving their Christian beliefs when presented with the secular viewpoint of science with the so called "truth" of evolution in early high school.

My opinion is that the age of the planet we call earth is one question. The age of the earth as defined in the Bible (Gen 1:14) is another question entirely.
Obviously, the writer of Genesis wasn't interested in the creation of our planet, or we would have some account of the origin of the core, mantle, crust, water, and air before the first statement of Gen 1:1. As it is, Genesis begins with water covering the earth and universal darkness. It is only on the third day that the earth receives its name since the waters then finally recede into their basins.
We can see that the 6-day creation account is only concerned with what normal people see when they look at their surroundings with their naked eyes. It isn't concerned with microscopic life, for example, seen only with scientific instruments.
To find the age of the Biblical earth we must go back to a time when the Holy Land (and the surrounding region) was completely covered with water and complete darkness prevailed. This suggests some time in the prehistoric past similar to the widely believed global flood occurring before c. 2300 BC.
Creation theories can be divided into two camps; 1) There was some kind of life on the planet prior to Gen.1:1; or 2) No life existed on the planet before Gen 1:1. There is no scientific evidence of the Holy Land being under water for at least millions of years in the past. This isn't conclusive because even a large asteroid or comet impact could cause temporary flooding of this nature, leading to the subsequent six-day creation events.
Since the bible makes no statement that no life of any sort existed before Gen 1:1, it is possible that some kinds of life did. If so, then the possible dates for the biblical earth's creation open up to much more recent times than explainable by science.
Two possible examples: c. 5700 BC, the date of the catastrophe which changed the Black Sea from fresh to salt water; c. 12,900 BC, the date of a hypothetical comet impact initiating the most recent, Holocene geological era.
So, in answering this question we need to decide at least two things:
1) Was there any life on the planet before Gen. 1:1?
2) Did any time elapse between the 6 days, and how much, if any?
Since scripture doesn't tell us, we await the answers we need from the Father, the Son, and the Holy Spirit.

A little over 6000 years old is my answer. God's Holy Word gives us the geneology and time line back to His creation.(Genesis 1-11) God's Word is Truth. "To Believe or Not Believe". (Genesis1-2) Satan has and continues to distort and deceive man into believing anything that is false:(Genesis 1-2) so, one of his most successful arenas is the subject of "Old Earth --vs-- Young Earth" and millions/billions of years --vs-- 6000+/- plus/minus a few years. Bottom line is this for me as a Child of God: God's Word is Truth and He gives us the geneology back to Adam and all of Creation. "For in six days, God created the heavens and the Earth...and all the fullness thereof." Then He rested on the seventh day."(Exodus 20:11) To me, it is simple. "Believe in God and Believe in His Holy Word, Genesis - Revelation!"
"Praise God we have a Savior!" And, His name is Jesus Christ!"
~~Andy~~

Are we over looking 2 Peter 3:8. One of God days is one (1) thousand years of man days according to this verse. I think the answer is most closely to 8 or 9 thousand inhabitable years, if we are using the formula of 1 of the Lord's day is 1 thousand man years since this is 2017 AD (ACE). God cannot be put in space and human time.

Based upon current scientific evidence, the earth is about 4.5 billion years old. Genesis 1:1 mentions the earth being created after the heavens. There is no time period associated with this introduction. So, how can we determine the age of the earth created in Genesis 1:1? In my opinion, this is a very important question for young people entering high school or college.
If they have been raised in a Church environment that has taught them from early on that the Earth is only 6 to 10 thousand years old, many will probably have problems with their faith when confronted with convincing evidence to the contrary. Some weather the storm of higher education but many do not. So, this discussion is for those who are struggling with their faith regarding the differing views between Science and what they have been taught that the Bible says about the earth’s age.
Since no one is directly inspired by God today we can only determine the age of the earth by what Science tells us or by what the Science of Linguistics tells us about translating ancient languages. So, no matter how you define it, Science of one sort or another is used to determine the Earth’s age.
In my opinion, the most significant support of the earth’s age is radiometric dating of rocks. If it were just a unique interpretation by scientists of experiments supporting the various ages of the rocks dated, that might be a basis for doubt. However, the radiometric dating method in some cases is self checking. If the data is questionable, a definitive answer can not be established. Additionally, there are many other means of cross-checking the findings of radiometric dates with other physical processes.
The absolute age of volcanic rocks can usually be determined because their radioactive clock is set to zero through the heating/cooling process during an eruption. This characteristic of volcanic rocks is important in verifying the accuracy of modern scientific dating methods.
For example, when a volcanic eruption occurs, it often spreads a layer of lava or ash over an area already being built up by sediments deposited layer after layer. After the eruption, sedimentary rocks continue to form as they did before, now burying the layer of lava. This eruption/burying sequence may continue for thousands of years.
Today, when geologists view an exposed cross section of this undisturbed formational sequence in an eroded valley, they have a means to verify the radiometric dates of the Lava by comparing them to the sedimentation rates of the intervening rock layers. For instance, one type of limestone forms in warm, shallow, quiet seas when a rich mixture of dissolved calcium combines with carbon and oxygen. This process is still occurring today.
Experiments have shown that it takes approximately 2,250 years to form one foot of such limestone. When such a process is sandwiched between two volcanic layers, you can compare the volcanic age difference between the top and bottom layers with the limestone formation rates in between. Top layers of lava consistently test younger than those below. Whenever there are age-datable materials within the sediments such as limestone, their ages also must fit in between the ages of the two confining lava layers. This check-and-balance system has proven to be reliable throughout the geologic column, along with several other testing methods that have also confirmed the dates assigned.
Based upon this system of dating and many others, it has been determined that the earth is about 4.5 billion years old. These ages also fit well within the creative framework contained in Genesis 1. Young people do not have to give up their faith in the Bible if they choose to believe the evidence of their eyes instead of a questionable interpretation of the Bible that conflicts with proven Scientific evidence.

I read most of the answers, specially Michael's answer. I had also been struggling with this question. And read the first few chapters of Genesis many many times comparing them with other related scripture passages. My conclusion is a little different.
I believe that six thousand years time does not tell the age of the earth, rather it tells about the years of human life from Adam to our time. I do not see that creation days are like our 24 hour days. Even Gen. 1:1-2:3 give a different evidence than 24 hour creation days. Here are some argument in favour of my conclusion.
1. On the first day of creation days, our days and night were made. This suggest that the first creation day must necessarily be longer than the day and night of 24 hour day.
2. The first three creation days had already passed without the sun, moon and stars that govern 24 hour days.
3. In Gen 2:17 God had warned Adam that the day he will eat the forbidden fruit the same day he would die. We know that Adam died at the age of 930 years. So the day in which Adam died must necessarily be longer than 930 years. More over, Adam is still living in his posterity, if we take book of Hebrews teaching that Levi was in Abraham's body when Abraham paid tithe to Melchizedech. So the day in which Adam ate the forbidden fruit is still running its course and it will keep running till Adam's posterity is living.
4. The seventh day of the creation week is not a 24 hour day. Because it has no ending like the other six days. It was still existing at the times of Joshua (Heb. 4:8), David (Ps. 95:11), and the writer of the book of Hebrews (Heb. 4:11), and it is still existing for us today (Heb. 4:9).
5. If creation days were 24 hour days then all the six days God was resting all 12 hour night times every day. In that case He would have not needed to rest on the seventh day. It is also odd that God would need only 24 hours rest. I believe, seventh day is eternal which is holy and blessed by God, in which He Himself has entered and that is a hope for us also to enter it.
6. When God entered the seventh day, all the creation especially humans remained in the sixth day of the creation week. Only after completion of their work they would have entered the seventh day as God did. So the sixth day is still running its course for humans.
7. I have come to believe that Gen. 1:1-2:3 is an introduction of God's plan for a humanity that will freely submit to His plan and act as His coworker. God's ultimate goal for this humanity is to enter into God's sabbath rest of seventh day and remain in His fellowship eternally. From Gen. 2:4 starts working out of God's plan, that ends at the end of Revelation ch. 20. And then the new humanity in Jesus Christ, created during Adam-Eve human history that had its beginning at Gen. 2:7, will enter God's sabbaths rest of seventh day. This human history is by now an history of 6000 years.
It is my understanding that Adam and Eve were created on the sixth day of the creation week after making of the land creatures. (I have used the word 'making' and not 'creating' for the simple reason that under the second creation activity, Gen. 1:21, God made the water creatures and the flying creatures on the fifth day of creation week and on the sixth day the land creatures.) And when they ate forbidden fruit they brought upon themselves along with their posterity the curse of eternal death. So we are living in an accursed sixth day of the creation week, unable to enter the holy and blessed seventh day in the fellowship of God. Thank God, Jesus our Lord entered this accursed sixth day and in Himself prepared a way out for us humans to enter the seventh day of Sabbath Rest. Praise the Lord.
I believe only human history by now is of 6000 years, and not the earth. According to this interpretation of mine the earth is much older than only 6000 years.